The lead aircraft of Patrol Squadron 9F was a Martin PM-1 (BuNo A-8300), a production version of the Naval Aircraft Factory's PN-12. On 30 October 1935 the red-tailed flying boat sported a gunnery award pennant and bombing "E" on its nose.

Historic Aircraft: The New Flying Boats

The "New" Flying Boats

During World War I-with the support of a fledgling aircraft industry-the U.S. Navy developed some excellent patrol flying boats. These included the only American-designed aircraft to see combat in the war as well as the NC series flying boats, with the NC-4 being the first aircraft to cross the Atlantic in 1919.

Immediately after that conflict, the emphasis in naval aviation was on carrier operations, and patrol-plane development was carried out on a very limited budget. Building on the F-5-L flying boat-developed from the British-designed Felixstowe F.5 aircraft-the Naval Aircraft Factory (NAF) in Philadelphia produced an improved version of the twin-engine flying boat, which was redesignated PN-5 in 1922.1 The designation PN-6 was used for two modified variants (originally F-6-L).

The single NAF-developed PN-7 was a much-improved aircraft, with new wings and an airfoil section, which provided increased lift. Two Wright 525-hp engines powered it. Although the wing design was successful, the engines were unreliable, and the wood hull required considerable maintenance.

The next two aircraft-designated PN-8-had two Packard 475-hp water-cooled V-12 engines and a metal hull. The subsequent PN-9 (converted from one of the PN-8s) and two newly built PN-10 aircraft were similar. The engines had problems-the Navy always preferred simpler, air-cooled engines-and radial engines were thus used to produce the later PN-12.

The PN-9, however, was a good performer. On 1-2 May 1925, Navy Lieutenants Clarence H. Schildhauer and James R. Kyle, on a test flight over Philadelphia, broke the world endurance record for Class C seaplanes by remaining aloft for 28 hours, 35 minutes, 27 seconds.

The following 1 September, the PN-9 took off from San Francisco for Pearl Harbor. With Commander John Rodgers-Naval Aviator No. 2-in command and navigating, and a crew of four, the aircraft was heavily laden with 1,278 gallons of fuel in its tanks and another 50 gallons in five-gallon cans. The plane nevertheless ran out of fuel and came down several hundred miles short of its destination. Despite an extensive air search, the PN-9 was lost at sea for ten days. Rodgers and his crew, meanwhile, improvised. Relying on their training as sailors, they fashioned a sail out of the lower wing's fabric and set out for Kauai Island. After covering about 450 miles they were sighted on 10 September by the submarine R-4 (SS-81) about ten miles short of their goal. Still, the aircraft had flown 1,841 statue miles, a record for Class C seaplanes that stood for almost five years.

Four PN-11 variants were built, with two engines being evaluated in the aircraft. The hull lines of the PN-11s marked the first major departure from the F-5-L design, featuring a wider hull that eliminated the sponsons, a feature of the older hull. The first aircraft was also fitted with twin vertical tail surfaces. (The last three aircraft were later designated XP4N.)

The two follow-on PN-12s represented the definitive design. Like its predecessors in the PN-series, the PN-12 was a biplane designed specifically for the patrol/antisubmarine role. Single .30-caliber machine guns were fitted in the bow and amidships, and four 230-pound bombs could be carried under the lower wing. Equally powered by twin 525-hp engines, one PN-12 had twin Pratt and Whitney Hornet R-1850s, and the other Wright Cyclone R-1750s. They gave the aircraft a top speed of 114 mph and a range at cruising speed of just over 1,300 miles. It was flown by a crew of five (in open cockpits), and a relief crew could be carried for long patrols. On 3-5 May 1928, the Cyclone-powered PN-12 set another world seaplane record, covering a distance of 1,243 statue miles in 17 hours, 55 minutes.

The Naval Aircraft Factory was not capable of large-scale production, and the Navy decided to have the PN-12 manufactured by private aircraft companies. The Douglas Aircraft Company produced 25 PD-1 aircraft and the Martin Company built 30 PM-1 variants based on the NAF design. Subsequently, Martin built 25 PM-2 variants and the Keystone Aircraft Corporation built 18 similar PK-1 aircraft, the latter being twin-rudder versions. Thus, the PN-12 gave birth to 98 offspring. These aircraft served in the Fleet until 1938.

In 1927 the Hall Aluminum Aircraft Company developed another PN derivative, the XPH-1.2 This was the first U.S. Navy flying boat to have all-metal stressed skin construction, which provided a considerable savings in weight. In the event, only ten PH-1s were built as the Navy moved to more advanced flying boat designs. But the Coast Guard procured seven improved Hall PH-2s and seven PH-3s for air-sea rescue missions. Some of these aircraft served into World War II.

Thus, the same basic flying boat design-from the F-5-L to the PH-3-spanned two world wars, a most notable achievement.

The designation F-5-L was derived from the British F.5, with the letter "L" indicating use of the American-built Liberty engine; PN-5 indicated Patrol aircraft, Naval Aircraft Factory, the fifth design.

2. See Swanborough and Bowers, United States Navy Aircraft, pp. 254-255.

The lead aircraft of Patrol Squadron 9F was a Martin PM-1 (BuNo A-8300), a production version of the Naval Aircraft Factory's PN-12. On 30 October 1935 the red-tailed flying boat sported a gunnery award pennant and bombing "E" on its nose.

U.S. NAVY

After literally sailing approximately 450 miles to Hawaii in September 1925, the PN-9 (BuNo A-6878) displays the effects of the sea voyage. Her crew stripped the lower wings of their fabric and fashioned sails after the flying boat ran out of fuel.